[276.] Æstivation was the fanciful name given by Linnæus to denote the disposition of the parts, especially the leaves of the flower, before Anthesis, i. e. before the blossom opens. Præfloration, a better term, is sometimes used. This is of importance in distinguishing different families or genera of plants, being generally uniform in each. The æstivation is best seen by making a slice across the flower-bud; and it may be expressed in diagrams, as in the accompanying figures.
277. The pieces of the calyx or the corolla either overlap each other in the bud, or they do not. When they do not overlap, the æstivation is
Valvate, when the pieces meet each other by their abrupt edges, without any infolding or overlapping; as the calyx of the Linden or Basswood (Fig. [277]).
Fig. 277. Diagram of a flower of Linden, showing the calyx valvate and corolla imbricate in the bud, etc.
Induplicate, which is valvate with the margins of each piece projecting inwards, as in the calyx of a common Virgin's-bower, Fig. [278], or
Fig. 278. Valvate-induplicate æstivation of calyx of common Virgin's-bower.